Revert "dracut-module-setup.sh: pass correct ip= param for ipv6"

This reverts commit 2f4149f276.

It is not proved to be right to get auto6 or dhcpv6 in 1st kernel,
pingfan is working on a dracut fix to do some fallback in 2nd kernel initramfs.
So revert this commit

dracut-module-setup.sh

@@ -293,12 +293,6 @@ kdump_setup_netdev() {
     _static=$(kdump_static_ip $_netdev $_srcaddr)
     if [ -n "$_static" ]; then
         _proto=none
-    elif is_ipv6_address $_srcaddr; then
-        if is_ipv6_auto $_netdev; then
-            _proto=auto6
-        else
-            _proto=dhcp6
-        fi
     else
         _proto=dhcp
     fi

kdump-lib.sh

@@ -310,18 +310,6 @@ is_atomic()
     grep -q "ostree" /proc/cmdline
 }
 
-# fixme, try the best to decide whether the ipv6 addr is allocated by slaac or dhcp6
-is_ipv6_auto()
-{
-    local _netdev=$1
-    local _auto=$(cat /proc/sys/net/ipv6/conf/$_netdev/autoconf)
-    if [ $_auto -eq 1 ]; then
-        return 0
-    else
-        return 1
-    fi
-}
-
 is_ipv6_address()
 {
     echo $1 | grep -q ":"